Copper Chemistry: Copper(I)-Cyanide HD

As potassium cyanide is added to a solution of Copper Sulfate a precipitate forms and a gas is being produced. As more Cyanide is added the precipitate dissolves again. Copper(II) and Cyanide undergo a reaction much like Iodide and thiocyanate. Copper gets reduced in this reaction forming the insoluble Copper(I)-Cyanide and the toxic gas Dicyane (CN)2. As more Cyanide is added a Tetracyanocuprate-complex forms much like Nickel does with Cyanide. This is why we filmed this experiment twice with different Copper concentrations. In the first part of the video a very conc. Copper(II) solution is used. It would take too much Cyanide to fully dissolve it so we use the first part to demonstrate the precipitated Cu(I)-Cyanide and the formation of Dicyanie which is clearly visible as gas bubbles out of the reaction. In the second video we use a diluted Copper(II) solution, here the gas evolution is hard to see but this time enough Cyanide can be added to demonstrate how the first insoluble Copper(I)cyanide dissolves again forming a complex.